This invention relates generally to wellbore casings, and in particular to wellbore casings that are formed using expandable tubing.
Conventionally, when a wellbore is created, a number of casings are installed in the borehole to prevent collapse of the borehole wall and to prevent undesired outflow of drilling fluid into the formation or inflow of fluid from the formation into the borehole. The borehole is drilled in intervals whereby a casing which is to be installed in a lower borehole interval is lowered through a previously installed casing of an upper borehole interval. As a consequence of this procedure the casing of the lower interval is of smaller diameter than the casing of the upper interval. Thus, the casings are in a nested arrangement with casing diameters decreasing in downward direction. Cement annuli are provided between the outer surfaces of the casings and the borehole wall to seal the casings from the borehole wall. As a consequence of this nested arrangement a relatively large borehole diameter is required at the upper part of the wellbore. Such a large borehole diameter involves increased costs due to heavy casing handling equipment, large drill bits and increased volumes of drilling fluid and drill cuttings. Moreover, increased drilling rig time is involved due to required cement pumping, cement hardening, required equipment changes due to large variations in hole diameters drilled in the course of the well, and the large volume of cuttings drilled and removed.
Conventionally, at the surface end of the wellbore, a wellhead is formed that typically includes a surface casing, a number of production and/or drilling spools, valving, and a Christmas tree. Typically the wellhead further includes a concentric arrangement of casings including a production casing and one or more intermediate casings. The casings are typically supported using load bearing slips positioned above the ground. The conventional design and construction of wellheads is expensive and complex.
The present invention is directed to overcoming one or more of the limitations of the existing procedures for forming wellbores and wellheads.
According to one aspect of the present invention, a method of operating an apparatus for radially expanding a tubular member including an expansion cone is provided that includes lubricating the interface between the expansion cone and the tubular member, centrally positioning the expansion cone within the tubular member, and applying a substantially constant axial force to the tubular member prior to a beginning of a radial expansion process.
According to another aspect of the present invention, a method of operating an apparatus for radially expanding and plastically deforming a tubular member including an annular expansion cone is provided that includes coupling the tubular member and the annular expansion cone to a support member, applying a substantially constant axial force of between about 500 to 2,000 lbf from the support member to the annular expansion cone to preload the annular expansion cone against the interior surface of the tubular member prior to the radial expansion and plastic deformation of the tubular member to seal the interface between the annular expansion cone and the tubular member, pumping a lubricant into the interface between the annular expansion cone and the tubular member, centrally positioning the annular expansion cone within the tubular member, and during the radial expansion and plastic deformation of the tubular member, displacing the annular expansion cone relative to the support member.